debugging python in visual studio , multiple versions of python

I am new to Python. I have an python project, I need to debug. The program was developed and run with an older version of python (2.7 or earlier) .
I have python 3.7 installed in my windows 7.
I want to install python 2 alongside python 3 and debug the program using python 2.

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virtualenv is a package that allows you to have different virtual environments on your machine.

A virtual environment can only be based on a python version that has been installed on your host.
So if you did not install python2 you can not create a python2 virtual envronment.

Within each environment you can install different python packages, (or different versions of it)

This would allow you for example to test if some code works with django 1.11 (you created one virtualenv in which you installed django 1.11)
and if it works as well with django 2.1 (another virtualenv in which you installed django 2.1)

If you have python2 and python3 installed on your host you can have virtualenvs with either poython2 or python3 as a abase.